Midday Movers: AAPL, KMX, MPC & More

Apple dragged down the tech sector amid supply concerns after China Labor Watch, a human rights group said that a Foxconn plant in China making the iPhone 5 was crippled by a strike. Foxconn denied the report.

CarMax soared following a bullish analyst report. ITG Investment Research has confirmed to CNBC that its analyst, John Tomlinson issued a “generally positive” report CarMax Monday but did not provide further details.

Marathon Petroleum shares hit a new 52-week high. The company announced plans to buy a refinery from BP , which would make Marathon the fourth-largest refiner in the U.S.

Barnes & Noble gained, helped by sales of its Nook tablet. In an interview on CNBC, CEO William Lynch said preorders are at "the highest levels we've ever seen for the Nook."

American International Group shares hit a 52-week high. In 2008, the insurance company was the beneficiary of a $182 billion bailout, the biggest federal government bailout of a private company in U.S. history.

Other stocks making new 52-week highs include Wal Mart Stores , 3M Company and Clorox .